GB2354051A - Torque transfer apparatus, wherein the engagement of each tooth portion includes a curved region - Google Patents

Abstract

A vertical louvre carrier truck, for use with a vertical louvre blind, includes a torque transfer apparatus. The torque transfer apparatus comprises a first body 110 mounted for rotation about a sleeve axis, the first body 110 including a plurality of equal length circumferentially spaced first teeth 114, and a second body 120 mounted for rotation about a second axis, the second body 120 including a plurality of equal length circumferentially spaced second teeth 124. The first and second teeth 114 and 124 both include an engagement portion which has a curved peripheral portion. A louvre blind having a plurality of louvre carriers is also disclosed.

Description

2354051 Torque Transfer ADparatus The present invention relates to a

vertical louver carrier truck including a torque transfer apparatus for use in a vertical blind.

It is known to transfer torque about a first rotational axis to torque about a second rotational axis wherein the two rotational axes are at an angle to each other using what are commonly known as bevelled gear wheels, wherein each of the bevelled gear wheels includes a frustoconical body portion which has extending perpendicularly from its surface a plurality of straight cut teeth. Two or more such bevel gear wheels are arranged so that they rotate about respective axes, the axes being at an angle (e.g. 900) to each other and such that the teeth of one of the wheels mesh with the teeth of the other of the wheels. Rotation of one of the bevel gear wheels (the drive wheel) about the first rotational axis thus causes rotation of the other bevel gear wheel (the pinion wheel) to generate torque about the second rotational axis.

Vertical louver blind carrier trucks which include at least one conventional straight cut bevel gear wheel are known from for example GB 2322153 (Harris), GB 2285829 (Harris) and US 4262728 (Levolor Lorentzen, Inc). However, problems arise with this sort of arrangement when the gear wheels are desired to be reduced in size. When a conventional straight cut bevel gear wheel is made smaller, the gear wheel teeth are reduced in size. However, the reduction in the size of the teeth significantly reduces their ability to transfer torque to a second gear wheel. This results in the bevelled gear wheel having an effective minimum size, beyond which any further reduction in size results in the teeth size being too small to enable the torque about the first axis to be transferred effectively to torque about 2 the second axis.

GB 1408080 (The Gleason Works) discloses a gear arrangement which uses teeth having a curved periphery to define an elliptical contact portion between two. interengaged teeth. However, the teaching of GB 1408080 is directed to the increased strength that can be attained with this type of gear. This document suggests that the gearwheels described therein are particularly suited to heavy duty applications involving high loads such as automotive differentials. There is no mention of the feature that similar gear wheels may be greatly reduced in size yet still retain teeth which have an effective contact area, allowing them to be used in applications where conventional straight cut gearwheels are inefficient at transferring torque owing to the relatively small contact areas of their teeth.

To overcome or ameliorate the above-noted problem with reducing the size of the components used in vertical louver blind carrier trucks, a new torque transfer apparatus is now proposed for use in such applications.

According to a first aspect of the invention there is provided a vertical louver carrier truck for a vertical louver blind, the carrier truck including a torque transfer apparatus for transferring torque about a first rotational axis to torque about a second rotational axis, the first rotational axis being at an angle relative to the second rotational axis, the apparatus including a first body mounted for rotation about the first rotational axis, the first body including a plurality of equal length ' circumferentially spaced first teeth, and a second body mounted for rotation about the second rotational axis, the second body including a plurality of equal length circumferentially spaced second teeth, wherein the chord length between adjacent first teeth is substantially 3 identical to the chord length between adjacent second teeth, and the first and second bodies are arranged such that an engagement portion of a first tooth is capable of engaging a respective engagement portion of a second tooth whereby rotation of the first body about the first rotational axis causes rotation of the second body about the second rotational axis, the engagement portion of each tooth including a curved peripheral portion to permit the inter-engagement of successive teeth upon rotation of the first body.

Thus, since the engagement portions of a first body tooth and a respective second body tooth both include a curved peripheral portion, the engagement portion of each tooth is generally elliptical in the sense that it is formed from two intersecting curves (it will be immediately apparent that the terms included herein do not denote a true ellipse according to a mathematical definition).

The advantage of the present torque transfer apparatus is that proper engagement between the first and second bodies can be maintained, even when both bodies are significantly reduced in size. This enables the present torque transfer apparatus to be used in such applications where the available space is limited, such as in vertical blind carrier truck assemblies. Being able to use smaller gearwheels allows the overall size of the carrier truck to be reduced.

The term "angle" is used herein to mean any angle other than 01 or 1801. Preferably the angle between the first and second axes is 5 to 175c', more preferably the angle is substantially 90'.

The curved peripheral portion of the teeth prevents the teeth of the first body fouling the teeth of the second 4 body and thus permits the successive engagement of teeth (i.e. permits the teeth to mesh). In a preferred embodiment, the engagement portion of each tooth includes two side walls and a topland surface therebetween, with the two side walls being mirror images of each other and each including corresponding curved peripheral edge portion. More preferably, the curved peripheral edge portions have a fixed radius (i.e. they are arcuate).

In a preferred embodiment, the topland surfaces of the teeth have a lengthwise convex curvature.

The height of the tooth preferably has its maximum at the portion of the tooth closest to the axis of rotation (i.e.

the proximal end of the tooth) and the height decreases along the curved peripheral portion of the tooth until it becomes zero at the distal end of the tooth. In a preferred embodiment, the side walls of the teeth each are in the form of a quadrant.

The first and second bodies are preferably made from an injection moulded plastics material. However, they may alternatively be made from a metal e. g. aluminium or steel.

The louver carrier preferably has a body suitable for slidable mounting in a header rail, a shaft on which a louver can be carried and an input sleeve for rotation by a drive rod, the body also including the torque transfer apparatus through which rotational movement of the sleeve causes rotationally movement of the shaft, the shaft and sleeve having rotational axes which are at least approximately laterally central of the body and perpendicular to each other. This type of arrangement avoids the disadvantage of known vertical louver blind constructions in which the rod and shaft are off set to opposite sides of the centre line of the header rail. In the present arrangement, rotation of the louver carrier about the axis of shaft (that is, about a vertical axis in normal use) has a minimal effect upon the position of the louver with respect to the header rail. 5 In preferred embodiments of the invention, the axis of rotation of the shaft typically approximately intercepts the axis of rotation of the drive rod.

The arrangement of the present invention also minimises the number of gears that are necessary. Known arrangements in which both the shaft and the sleeve rotational axes are approximately laterally central of the body include a plurality of gears. In particular, these known arrangements include an external worm gear on an outer cylindrical surface of a sleeve, a spur gear on the shaft and an intermediate idler gear which is in mesh with both the worm gear and the spur gear. The present arrangement includes just two gears in mesh with each other, one of which is carried on the sleeve and the other of which is carried on the shaft. The present arrangement is thus far more compact and less complex than known apparatus. It is therefore cheaper and easier to assemble louver carriers according to the second aspect of the present invention than known louver carriers.

In a second aspect of the invention, there is provided a louver blind including a plurality of louver carriers according to the first aspect of the present invention. The louver carriers are typically slidably mounted in a header rail. Preferred embodiments further comprise a drive rod engaged with a drive sleeve of each of the louver carriers for rotation of the sleeve and thus rotation of the louver.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying 6 drawings, in which:

Figure 1 is a view of a torque transfer apparatus which may be used in louver carrier trucks according to the first 5 aspect of the invention; Figure 2a is a view of one of the gear wheels of the apparatus of figure 1; Figure 2b is an axial sectional view through the gear wheel shown in figure 2a; Figure 3a is a view of the other of the gear wheels of the apparatus of figure 1; Figure 3b is an axial sectional view of the gear wheel shown in figure 3a; Figure 4 is a sectional view of a louver carrier truck which embodies the first aspect of the present invention; and Figure 5 is a cross- sectional view of the louver carrier truck shown in figure 4.

Figure 1 shows a torque transfer apparatus 2 which consists of a drive wheel 4 in engagement with a pinion wheel 6. The drive wheel 4 is mounted for rotation about a first axis 14 and the pinion wheel 6 is mounted for rotation about a second axis 24. The first axis 14 and the second axis 24 are arranged such that they intersect one another and are perpendicular to each other. The drive wheel 4 is shown in more detail in figures 2a and 2b and the pinion wheel-6 is shown in more detail in figures 3a and 3b.

Drive wheel 4 consists of a shaft 8 and a circular plate 7 portion 10 extending radially outwards from one end thereof. The circular plate portion 10 has a planar surface 11 facing away from the shaft 8. Extending axially from the planar surface 11 and radially outwards from the first axis of rotation 14 are twelve teeth 12. All of the teeth 12 are the same length and are equally spaced about the first axis 14, such that the angle "X" between adjacent teeth 12 is the same (i.e. 30') This arrangement results in a constant chord length C, between adjacent teeth 12, the chord length C, being a function of the number of teeth 12 and the diameter of the circular plate portion 10. More specifically, as there are twelve teeth 12 and the diameter of the drive wheel 4 is 10.5mm and the chord C, is approximately 2.75mm.

Each tooth 12 includes a curved peripheral edge portion 13 which has a constant radius of 3mm. Thus, as shown in figure 2b, each of the teeth 12 has a cross-sectional shape which approximates to a quarter of a circle. Each tooth 12 has two side portions 40a, 40b which are joined by a convex topland surface 42.

Figures 3a and 3b show in more detail the configuration of the pinion wheel 6 which consists of a shaft 18 and a circular plate portion 20 extending radially outwards from one end thereof. The circular plate portion 20 has a planar surface 21 facing away from the shaft 18. Extending axially from the planar surface 21 and radially outwards from the second axis rotation 24 are eight teeth 22. All of the teeth 22 are the same length and are equally spaced about the second axis 24, such that the angle "Y" between adjacent teeth 22 is the same (i.e. 450). This arrangement results in a constant chord length C2 between adjacent teeth 22. The pinion wheel 6 has eight teeth 22 and a diameter of 7.Omm, therefore the chord C2 is also approximately 2.75mm.

8 Each tooth 22 includes a curved peripheral edge portion 23 which has a constant radius of 3mm. Thus, as shown in figure 3b, each of the teeth 22 has a cross-sectional shape which approximates to a quarter of circle. Each tooth 22 has two side portions SOa, SOb which are joined by a convex topland surface 52.

Figures 4 and S show an embodiment of the second aspect of the invention, namely a louver carrier including a torque transfer apparatus described above. Figure 4 shows a louver carrier 100. Figure 5 shows the louver carrier 100 carried in a header rail 200.

For the avoidance of doubt, it should be noted that in the following description, references to "up", "down", and to related terms, refer to the orientation that the components of the blind adopt when installed for normal use, as they are shown in the figures.

With reference to figure S, a louver blind embodying the second aspect of the invention includes a header rail 200.

The header rail 200, typically formed as an elongate aluminium. extrusion of uniform cross-section, has spaced parallel side walls 201. From each side wall 201, a respective flange 202 projects towards the opposite side wall 201, the flanges 202 being substantially coplanar. For use, the header rail 200 is disposed with its flanges horizontal.

The louver blind further includes a plurality of louver carriers 100. Each louver carrier has a body 101 (shown in section in figure 4), formed as an injection moulding of plastic material. The louver carrier 100 is shaped externally so that it has a width which is a close fit within the header rail 200 and a length, in the axial direction of the header rail 200, which is comparatively 9 smaller. A slot 102 is formed in opposite side walls of the body 101. Upon assembly of the blind, each flange 202 enters within a respective slot 102 to support the body and to allow it to slide with respect to the header rail 200, the side walls of the body 101 being adjacent and parallel to the side walls 201 of the header rail 200. Adjacent louver carriers are interconnected by spacer links (not shown). The spacer links permit adjacent louver carriers 100 to closely approach one another within the header rail, but limit the maximum distance by which adjacent louver carriers 100 can slide apart from one another. Thus, by drawing an end one of the louver carriers 100 (referred to as "the lead carrier") along the length of the header rail 200, the other louver carriers 100 will follow it, with all of the louver carriers 100 being equally spaced from one another by a distance determined by the length of the spacer links.

A hook formation 131 projects downward from a bottom surface of the louver carrier 100. A respective elongate louver (not shown) of fabric, wood, or other material is suspended from each hook 131 by means of an intermediate louver header (not shown).

A metal drive rod 1SO extends the length of the header rail 200, passing through each of the louver carriers. A user control, typically a loop of chain carried on a chain wheel, allows a user to rotate the rod. Rotation of the rod is conveyed by a torque transfer apparatus within each louver carrier 100 to cause rotation of its hook 131 and, therefore, to the louver hanging from it.

Those familiar with this technology will recognise that the above paragraphs describe features which this embodiment of the invention shares with known louver blind systems. Further features of significance to the present invention will now be described in further detail.

A drive wheel 110 including a circular plate portion 112 and teeth 114 essentially as described above in connection with the drive wheel 4 is attached to a sleeve 156. A radially extending flange 159 is carried on the outer surface of the sleeve 156 close to one of its ends, there being a short portion 155 of the sleeve projecting axially beyond -the flange 159. Instead of the shaft 8 of the drive wheel 4, the drive wheel 110 includes a short tubular portion 157 which projects axially away from the circular plate portion 112. The interior diameter of the tubular portion 157 is substantially identical to the interior diameter of the sleeve 156. The drive wheel 110 and the sleeve 156 are arranged such that the tubular projecting portion 157 of the drive wheel 110 and the projecting sleeve portion 155 of the sleeve 156 project through suitably placed circular holes 151, 153 formed through front and rear walls 106, 108 of the body 100 such that the projecting portions 155, 157 act as journals borne within the holes 151, 153. The flange 159 and the circular plate portion 112 restrict axial movement of the drive wheel 110 and sleeve 156 within the body.

As mentioned above, the louver carrier 100 includes the hook component 131. An upper part of the hook component 131 is formed as a pinion wheel 120 of circular outline. The pinion wheel 120 is substantially the same as that described above with respect to pinion wheel 6. The pinion wheel 120 has vertically-extending gear teeth 124. Below the gear teeth 124, there is a circular plate portion 122 from which the gear teeth 124 extend. A shank 143 extends downward from the plate portion 122, the hook portion 131 extending from the shank 143. The shank 143 and the hook portion 131, when viewed end-on, have a circular profile. A slot 134 extends diametrically through the shank 143 and the hook portion 131 along part of their lengths, to form 2 spaced legs. A rib 135 projects from the shank 143 close to the upper extent of the slot 134, the rib having a chamfered lower surface 137.

The hook component 130 is arranged in the louver carrier body 101 so that its hook portion 131 and part of its shank 143 pass through a hole 141 formed centrally through a lower wall of the body 101 so that the hook component 131 projects downwardly from the body. The rib 13S is of a radius greater than that of the whole. Upon insertion of the hook component 130, the chamfer 137 on the lower surface of the rib 13S engages with the material of the body 101 surrounding the hole 141, thereby forcing the legs of the hook component 130 to close together by a small distance and which allows the rib 13S to pass through the hole 141. Once the rib 135 has emerged from the bottom of the hole 141, the leg springs resiliently apart such that the rib 13S abuts the lower surface of the body 101 so as to resist removal of the hook component 130 from the body 101.

When the hook component 130 is so arranged in the body 100, its plate portion 122 lies in contact with a flat upwardly directed circular bearing surface 140 formed in the interior of the body 101.

The hook component 130 may include a stop peg (not shown) and the bearing surface 140 may include a rebate (not shown) so that the stop peg can move within the rebate, but such that it comes into contact with the material of the body 101 at the end points of the rebate. This arrangement limits the extent to which the hook component 130 can rotate and ensures that the hook component 130 and therefore the louver attached to it are constrained to rotate only between fixed end points.

12 The teeth 124 of the pinion gear 120 are arranged to mesh with the teeth 114 of the drive wheel 110.

The metal drive rod 1SO includes 3 longitudinal channels 152 which are equally spaced about the circumference of the rod 1SO. Each channel 152 is engaged by a respective lobe 1S4 which projects inwardly of the sleeve 156 so that rotation of the rod 1SO causes rotation of the sleeve 1S6 and thus rotation of the drive wheel 110. Rotation of the drive wheel causes the pinion wheel, and thus the louver connected to it, to rotate.

The sleeve may be provided with a clutch mechanism so that if a predetermined torque limit is exceeded, the drive wheel 110 will not be rotated. This allows all of the louvers in the blind to be brought into alignment with one another as is well known by those skilled in this technical field.

These preferred embodiments have been described by way of an example and it will be apparent to those skilled in the art that many alterations can be made that are still within the scope of the invention.

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Claims (7)

1. A vertical louver carrier truck for a vertical louver blind, the carrier truck including a torque transfer apparatus for transferring torque about a first rotational axis to torque about a second rotational axis, the first rotational axis being at an angle relative to the second rotational axis, the apparatus including a first body mounted for rotation about the first rotational axis, the first body including a plurality of equal length circumferentially spaced first teeth, and a second body mounted for rotation about the second rotational axis, the second body including a plurality of equal length circumferentially spaced second teeth, wherein the chord length between adjacent first teeth is substantially identical to the chord length between adjacent second teeth, and the first and second bodies are arranged such that an engagement portion of a first tooth is capable of engaging a respective engagement portion of a second tooth whereby rotation of the first body about the first rotational axis causes rotation of the second body about the second rotational axis, the engagement portion of each tooth including a curved peripheral portion to permit the inter-engagement of successive teeth upon rotation of the first body.

2. A vertical louver carrier truck according to claim 1, wherein the angle between the first and second rotational axes is from 5 to 175', preferably substantially 90'.

3. A vertical louver carrier truck according to claim 1 or claim 2, wherein the curved peripheral portion of each tooth has a fixed radius.

4. A vertical louver carrier truck according to any preceding claim, wherein each tooth includes two side walls 14 having a curved peripheral edge portion and a topland surface therebetween, the topland surface having a lengthwise convex curvature.

5. A vertical louver carrier truck according to any preceding claim, the louver carrier having a body suitable for slidable mounting on a header rail, a shaft on which a louver can be carried and an input sleeve for rotation by a drive rod, the body also including the torque transfer apparatus through which rotational movement of the sleeve causes rotational movement of the shaft, the shaft and sleeve having rotational axes which are at least approximately laterally central of the body and perpendicular to each other.

6. A louver blind including a plurality of louver carriers according to any preceding claim.

7. A vertical louver carrier truck or a louver blind including a plurality of such louver carrier trucks, substantially as described herein with reference to the accompanying drawings.